Multiple choice

Two pipes A and B can fill a tank in 38 mins and 57 mins respectively. How much time after opening both taps, the tap A should be turned off so that tap B may take 12 min more to fill the tank?

  1. 12 min

  2. 16 min

  3. 15 min

  4. 18 min
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let both taps open for t minutes, then B works alone for 12 more minutes. Combined rate = 1/38 + 1/57 = 5/114. Work done: (5/114)t + (1/57)*12 = 1. Solving: 5t + 24 = 114, so t = 18 minutes.

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